=jdk9,str JDK9 ready classes, in special directories (#23650)

* =jdk9,str JDK9 ready classes, in special directories

* =str,jdk9 prepare for releasing using JDK9 (needs sbt 1.0+ though)

* =str,jdk9 passing TCK spec touching some JDK9 types internally

* make sure to include linting options

akka-stream-tests/src/test/java-jdk9-only/akka/stream/javadsl/JavaFlowSupportCompileTest.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2017 Lightbend Inc. <http://www.lightbend.com/>
+ */
+
+package akka.stream.javadsl;
+
+import akka.NotUsed;
+import akka.japi.Pair;
+import org.junit.Test;
+
+import java.util.concurrent.Flow;
+
+public class JavaFlowSupportCompileTest {
+  @Test
+  public void shouldCompile() throws Exception {
+    final Flow.Processor<String,String> processor = new Flow.Processor<String, String>() {
+      @Override
+      public void subscribe(Flow.Subscriber<? super String> subscriber) {}
+      @Override
+      public void onSubscribe(Flow.Subscription subscription) {}
+      @Override
+      public void onNext(String item) {}
+      @Override
+      public void onError(Throwable throwable) {}
+      @Override
+      public void onComplete() {}
+    };
+
+
+    final Source<String, Flow.Subscriber<String>> stringSubscriberSource = 
+      JavaFlowSupport.Source.asSubscriber();
+    final Source<String, NotUsed> stringNotUsedSource = 
+      JavaFlowSupport.Source.fromPublisher(processor);
+
+    final akka.stream.javadsl.Flow<String, String, NotUsed> stringStringNotUsedFlow = 
+      JavaFlowSupport.Flow.fromProcessor(() -> processor);
+    final akka.stream.javadsl.Flow<String, String, NotUsed> stringStringNotUsedFlow1 = 
+      JavaFlowSupport.Flow.fromProcessorMat(() -> Pair.apply(processor, NotUsed.getInstance()));
+
+    final Sink<String, Flow.Publisher<String>> stringPublisherSink = 
+      JavaFlowSupport.Sink.asPublisher(AsPublisher.WITH_FANOUT);
+    final Sink<String, NotUsed> stringNotUsedSink = 
+      JavaFlowSupport.Sink.fromSubscriber(processor);
+  }
+}